This present invention is especially designed to measure ultra small leaks in large capacity liquid tanks. This invention is designed to measure very small leaks from very large capacity tanks such as the ability to measure one (1) gallon out of a total inventory of a two million gallon tank. This is especially important in the area of detecting the leaking of storage tanks.
The most common technique used by the prior art to measure product level is a float which rides on the surface of the product. However, this approach is susceptible to a multitude of mechanical problems which limits its use as an ultra high accuracy sensor. In general, the prior art float type transducers associated with floats are limited in the range of 0.007 inches of movement before they can give a reading or, about fifty (50) gallons of change in large tanks before they read.
Other techniques used for level sensing, such as deferential pressures or interfaced detections, can offer slightly better accuracy under specific circumstances, but these are also not accurate enough to meet the proposed requirements set by environmental agencies.
There have been many examples of prior art which have tried to solve this problem but generally the accuracy of these leak detecting meters are no greater than fifty (50) gallons in two million and such leakage is unacceptable in terms of the current environmental standards.
Much of the prior art attempted to utilize pressure changes caused by the movement of the fluid in some kind of a tube to activate a diaphragm upon the change of fluid flow or level. While this may be reasonably accurate under very controlled conditions, in the normal conditions of a storage tank, it is not successful. The reason it is not successful is because in normal storage tanks you have extreme conditions of temperature and various vapor levels for various products which could have a significant impact on the accuracy of the meter. Further, attempting to read vapor pressure and changes in the pressure above based on the movement of the liquid below provides for additional inaccuracies as the vapor is more compressible and more subject to error because of its compressibility than is measuring the fluids motion itself.